Methods for manufacturing super micro fibers

ABSTRACT

Methods for manufacturing super micro fibers to produce fibers having dimensions of between 0.003-0.003 denier per filament. The manufacturing methods include the following steps: blending polyamide and polyester compounds; passing the polyamide-polyester mixture through twin-screw extrusion; spinning the mixture and; melting, dissolving and removing the polyester compounds with alkaline solvents.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to novel and unique methods for manufacturing super-micro fibers. More specifically, this invention relates to methods for manufacturing super-micro fibers using single-path, twin-screw extrusion processes to produce super-micro fibers having dimensions between 0.003-0.0003 denier per filament.

[0002] Super-micro fibers are very thin fibers with silk-like properties. Thinner than silk, they are much more durable, less brittle and less sensitive to environmental factors, such as corrosion and moisture, etc. Super micro fibers are used in the fashion industry to produce sportswear and other forms of sport attires. These fibers have also been used in the electronic industry and other industrial applications seeking to avoid the traditional wear and tear associated with other fibers usage.

[0003] Generally, super micro fibers are manufactured by combining, blending and extruding two or more polymers. The final products, the super micro fibers, are subsequently obtained by dissolving one of the polymers from the other with a solvent. As starting materials, generally the polymers used are polyesters, copolyesters, polyamides and copolyamides.

[0004] Examples of polyesters, copolyesters, polyamides and copolyamides are disclosed in U.S. Pat. No. 5,555,716. The examples of which are incorporated by reference in their entirety. Polyamides and copolyamides are well known by the general term “nylon” and are long-chain synthetic polymers containing amide (—CO—NH—) linkages along the main polymer chain. Typical polyamides include nylon 6, nylon 6/6, nylon 6/10, nylon 6/12, nylon 6T, nylon 11, nylon 12, and copolymers or mixtures thereof. Polyamides can also be copolymers of nylon 6 or nylon 6/6 and a nylon salt obtained by reacting a dicarboxylic acid component such as terephthalic acid , adipic acid, or sebacic acid with a diamine such as hexamethylene diamine.

[0005] Suitable polyesters and copolyesters include, for example, those prepared by the condensation of aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalene-2,6-carboxylic acid, aliphatic dicarboxylic acids such as adipic acid or their esters with diol compounds such as ethylene glycol and diethylene glycol. Preferred polyesters include polyethylene terephthalate and polybutylene terephthalate.

[0006] Because manufacturing of super micro fibers is highly specialized, the types of manufacturing processes used are sure to influence the overall cost of production and, more importantly, the desired dimensions of the super micro fiber products. Republic of China (Taiwan) Patent Nos. 177413 and 168750 disclosed processes for manufacturing super-micro fibers by using polyesters and polyamides as raw materials. The processes utilized a special spinneret plate design to spin the polyamide-polyester complex. The complex was melted and one polymer was removed to produce the micro fibers. Such processes are limited by the spinneret plate design. A single orifice of such a design arrangement can only have 37 partings, resulting in the production of micro fibers with filaments dimensions of around 0.025 denier.

[0007] Japan Patent Publication Nos. 40-9429, 41-7886, 41-7893, 51-6261 disclosed processes for manufacturing super micro fibers aimed at obtaining thinner fibers. These patents collectively disclosed blending polyamide or polyester with polyethylene (PE), polypropylene (PP), or polystyrene (PS) granules. The blended mixture is spun, the continuous phase is melted and removed by solvents to obtain the super micro fibers. These processes used solvents, such as xylene and toluene to dissolve the PE and PP components (the continuous, sea-phase components) from the polyamide components (stationary, island-phase, super micro fiber products). A major draw-back of such processes is that solvents like xylene and toluene are known to cause serious damage to the environment, are hazardous to humans and other life forms and are relatively expensive.

[0008] Other prior arts are known to use polyamide and polyethylene terephthalate as raw materials for producing super micro fibers. These processes, along with the processes discussed above are not known to use affinity components to hold the polyamide and the polyester compounds, prior to and during blending, let alone using affinity components at a desired percentage weight of total mixture to achieve super micro fiber product with dimensions between 0.003-0.0003 denier per filament. These processes usually encounter difficulties in blending and spinning the polyamide-polyester mixture, just to mention a few.

[0009] As an example, Japan Patent Publication No. 8-27626 disclosed a method for producing super micro fibers that combines polyamide and polyethylene terephthalate, which are then spun at high temperature for quite a long time, so as to produce the desired super micro fibers primarily containing polyamide. This process lacks an affinity mixture component. Therefore, processing requires blending and spinning at a high temperature for a considerable length of time to increase the affinity between the polyamide and the polyethylene terephthalate. However, the processing time for blending and spinning in practice is not long enough to enhance affinity prior to pyrolosis. That is, continuous blending and spinning at high temperature results in serious pyrolosis, thereby affecting the spinning characteristics of the micro fibers and the quality of the yarn.

[0010] Prior to this present invention, none of the existing prior arts, individually or collectively, have disclosed a method for making super micro fibers by blending polyamide-polyester mixture, adding an affinity mixture to hold the polyamide-polyester mixture during blending and spinning, using single-path twin screw extrusion processes to extrude the mixture, spinning the mixture, performing drawing processes of the mixture, and dissolving the polyester components to obtain the polyamide, super micro fiber components of dimensions between 0.003-0.0003 denier per filament.

[0011] Accordingly, it is an objective of this invention to provide methods for manufacturing super micro fibers using an affinity mixture for holding the polyamide and polyester compounds together prior to and during blending and spinning.

[0012] Another object of this invention is to provide relatively cheaper methods for manufacturing super micro fibers by using single path-twin screw extrusion processes and operating at temperatures much lower than the prior arts processes to produce thinner super micro fibers with dimensions between 0.003-0.0003 denier per filament.

[0013] It is a further object of this invention to provide processes for manufacturing super micro fibers using less toxic solvents, such as alkaline base solvents to dissolve the sea-phase polyester components from the polyamide-polyester complex to form the island-phase polyamide, super micro fibers components.

[0014] Still, it is a further object of this invention to use precise weight percentages of mixture components, precise ranges of melting viscosity ratios, precise ranges of addition ratios, minimum intrinsic viscosities, precise ranges of spinneret packed pressures and take-up velocities to form steady island-phase polyamide, super micro fiber structures.

[0015] These objectives which are achieved by the present invention can be further discerned from the foregoing description.

SUMMARY OF THE INVENTION

[0016] The present invention provides methods for manufacturing super micro fibers with dimensions between 0.003-0.0003 denier per filament. The micro filaments are produced by blending polyamide and polyester mixtures, performing single path twin screw extrusion of the blended polyamide-polyester mixture complex, spinning the mixture complex, and performing drawing processes of the mixture complex. Finally, the complex is melted, dissolved and the sea-phase polyester components are removed from polyamide-polyester complex to form the island-phase, super micro fibers.

[0017] More specifically, the present invention uses polyamide and polyethylene terephthalate as starting materials, along with an affinity mixture containing terephthalic acids, ethylene glycol and 5-sodium sulfodimethyl isophthalate compounds. Additionally, these present inventive methods use viscosity control, spinneret package pressure and take-up velocities of the polyamide-polyester mixture complex to produce super micro fibers of desirable dimensions.

DESCRIPTION OF THE FIGURES

[0018]FIG. 1: Shows electron-scanned microscope photography of Nylon 6 super micro fibers with dimensions of between 0.0014-0.003 denier per filament.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention relates to processes for manufacturing super micro fibers.

[0020] Specifically, the present invention relates to processes for manufacturing super micro fibers of dimensions between 0.003-0.0003 denier per filaments. Polyamide-polyester mixtures are combined with an affinity copolyester mixture and passed through single path twin-screw extrusion processes. By controlling the spinneret packed pressures and the polyamide-polyester complex mixture's take-up velocities super micro fibers of desirable dimensions are produced. The processes use a polyamide (“Component A”) preferably 30-50% by weight, a copolyesters component (“Component B”) preferably between 40-75% by weight and an affinity copolyester component (“Component C”) preferably between 5-10% by weight as raw materials.

[0021] Component B is a granules mixture of terepthalic acids, ethylene glycol with diol and di acids or isophthalate compounds. Component B is added to the polyamide-polyester complex mixture at an addition ratio of between 5-40% per mole to decrease the melting point and melting viscosity of the polyamide-polyester complex during processing, while maintaining the desired molecular weight of the polyester to maintain the strength of the spun micro fibers after processing is complete.

[0022] Maintaining the intrinsic viscosity of Component B during processing to ≧0.5 enhances its melting viscosity during manufacturing. If the addition ratio of Component B is greater than 40% per mole, the polyester suffers premature phase separation from the polyamide-polyester complex. If the melting point of the polyester (Component B) is so low because the addition ratio is lower than 5% per mole may result in the polyamide-polyester complex being difficult to crystalize, and may cause the fiber to adhere to each other during processing.

[0023] The copolyester affinity mixture (Component C) of the present invention comprises terepthalic acid and ethylene glycol to which 5-sodium sulfodimethyl isophthalate is added, preferably, between the ratios of 0-1.0% per mole. The copolyester affinity mixture component serves to enhance the affinity between the polyamide (Component A) and the copolyester (Component B). The affinity between the components is achieved when sulfonic acids groups from the mixture containing the copolyesters polarize and absorb the polyamide thereby resulting in an enhanced degree of affinity.

[0024] Experiments have shown that an affinity mixture containing more than 1% per mole of the 5-sodium sulfodimethyl isophthalate results in the radii and the pitches of the island-phase, polyamide components of the polyamide-polyester complex, prior to removing the polyester sea-phase components, being considerably small. Having pre-separation island-phase components with radii and pitches smaller than desired create difficulties in separating the sea-phase components from the island-phase components to obtain the desired super micro fibers. To obtain steady polyamide island-phase components and more fluid polyester sea-phase components, one has to control the blending ratios, weight compositions and melting viscosity ratios of the polyamide component (Component A), the polyester component (Component B), and the affinity polyester mixture (Component C).

[0025] In general, components with the higher viscosity are apt to become the island-phase and components with lower viscosity are apt to become the sea-phase and are more mobile or fluid. This invention desires to have increased number of island-phase components during processing to decrease losses resulting from melting, dissolving and removing the sea-phase components to form the super micro fibers. To accomplish the latter, the melting viscosity ratios of the island-phase components are raised considerably. In contrast, the copolyesters (Component B & C) should possess a low melting viscosity ratio so as to be effectively removed. Therefore, the melting viscosity ratios of the copolyesters to that of the polyamide must be maintained within a certain range to enable the polyamide to form an island-phase during and after separation. A desired melting viscosity ratio of the polyamide and polyester components during processing temperature should preferably exist between 4-10.

[0026] In a preferred embodiment, super micro fibers are manufacture by blending Component A, Component B and Component C. The blended mixture is then passed through single path twin-screw extrusion processes until a satisfactory degree of extrusion is achieved. Unlike double path extrusion, which uses separate extruders, the single path processes are economical and result in thinner super micro fibers. The polyamide-polyester mixture containing the affinity mixture component is spun, and subsequently placed through drawing processes. Final super micro fibers of between 0.003-0.0003 denier per filament are achieved by dissolving the more viscous sea-phase polyester components (Components B & C) of the polyamide-polyester complex to form the island-phase, polyamide super micro fiber components. Alkaline solvents are used to dissolve the sea-phase from the island-phase, such as NaOH rather than toluene and xylene as used in the prior arts. Alkaline solvents are less toxic to the environment, humans and other life forms. Spinning is usually performed at a spinneret packed pressure of between 70-130 kg/cm² and the polyamide-polyester complex take-up velocities set between 600-1500 m/min.

[0027] In a second preferred embodiment, the polyamide-polyester mixture containing Components A & B are blended with 5-10% by weight of Component C, passed through single path, twin-screw extrusion processes, spun for a desired time and passed through series of drawing processes. The island-phase polyamide super micro fiber components, preferably between 0.003-0.0003 denier per filament, are obtained by dissolving the sea-phase more viscous polyester components (Component B & C) to form the island-phase, polyamide super micro fiber components. Like the Previous embodiment, spinning is performed at a spinneret packed pressure of between 70-130 kg/cm² and the polyamide-polyester complex take-up velocities set between 600-1500 m/min.

[0028] In a third preferred embodiment, which is the best mode of the invention, super micro fibers are produced having a dimensions of between 0.003-0.0003 denier per filament by blending the following:

[0029] (1) 30-50% by weight of polyamide compound mixture (Component A). Having a polyamide mixture of 30-50% by weight of the total weight of the polyamide-polyester complex is sure to avoid unexpected consequences, such as the presence of the sea-phase components in the island-phase and the island-phase components existing in the sea-phase. Polyamide by weight of over 50% of the total weight of the polyamide-polyester complex often results in the existence of the sea-phase component in the island-phase component and vice versa. Similarly, having a polyamide mixture less than 30% by weight of the entire polyamide-polyester mixture often results in the production of thicker super micro fibers than desired, and the desired dimensions of 0.003-0.0003 denier per filaments are often not realized; and

[0030] (2) 40-65% by weight mixture of copolyester (Component B). Having a copolyester mixture of between 40-65% per weight of the total weight of the complex have being shown to produce desired super micro fibers of between 0.003-0.0003 denier per filament. Having this range by weight of Component B has prevented unexpected circumstances, such as having the sea-phase component existing in the island-phase and vice versa, doing and after final production of the super micro fibers; and

[0031] (3) 5-10% by weight of a copolyester affinity mixture (Component C). The percent concentration of the isophthalate compound of the affinity mixture is preferably less or equal to 1%. Having the affinity mixture over 10% by weight of the total polyamide-polyester complex often results in having the island-phase radius and pitch components of the super micro fibers being considerable smaller than desired. Small island-phase radii and pitches increase difficulties in separating the copolyesters mixture components (Component B & C) from the polyamide component (Component A) during the melting, dissolving and removing phases of the process. Similarly, having an affinity mixture less the 5% by weight of the total complex mixture often results in uneven distribution between the polyamide and the copolyester components.

[0032] To enhance distribution, the melting viscosity of the affinity mixture is controlled. The subsequent blended mixture containing 30-50% by weight of polyamide compound (Component A), 40-65% by weight of copolyester (Component B) and 5-10% by weight of the copolyester affinity mixture (Component C) containing terepthalic acid acids, ethylene glycol, 5-sodium sulfodimethyl isophthalate compounds of preferably less or equal to 1% is subsequently passed through single, path twin-screw extrusion processes.

[0033] The resulting products are spun and passed through drawing processes. The subsequent products are melted and dissolved. The sea-phase polyester components comprising the 40-65% by weight of copolyester and the 5-10% by weight of the affinity mixture are melted, dissolved and removed resulting in island-phase, super micro fiber components of dimensions between 0.003-0.0003 denier per filament.

[0034] The 40-65% by weight copolyester (Component B) is added to the entire mixture and has addition ratios of between 5-40%. Holding the intrinsic viscosity of the 40-65% by weight copolyester mixture to greater than 0.5 aids in the production of super micro fibers of dimensions of between 0.003-0.0003 denier per filaments. The process of this embodiment is performed at a spinneret pack pressure of 70 kg/cm² and the polyamide-polyester take-up velocities of between 600-1500 m/min.

[0035] The intrinsic viscosity of the copolyester mixture was determined by the use of phenol-/m-cresol. The analysis method used a phenol-/m-cresol solvent having a polymer concentration of 0.5 grams/100 ml solution, which was analyzed at room temperature. By way of examples, the manufacturing methods and mixture components of the present invention may be as follows:

EXAMPLE I

[0036] 50% by weight of Nylon 6 (Component A) with relative viscosity of 2.47. The viscosity is measured using 1% weight sulfuric acid. 45% by weight of copolyester (Component B) polyethylene terephthalate (PET) and 13% per mol of adipic acid. The intrinsic viscosity of the component B is 0.508. The melting viscosity is 365 poise at 270° C. 5% by weight copolyester (Component C) containing polyethylene terephthalate (PET), 10% per mol of isophthalic and 0.3% per mol of 5-sodium sulfodimethyl isophthalate. Component C has an intrinsic viscosity of 0.503.

[0037] These three components/granules are mixed in a rolling barrel mixer and dried; they are then melted and blended using a single twin-screw extruder having L/D=36 and D=37 mm at 270° C. The blended granules are dried with nitrogen gas at 130° C. for eight hours and subsequently spun at 265° C. The spinneret pack pressure is 74 kg/cm². The spinneret plate has 484 holes. The L/D of the spinneret hole is 0.5 mm/0.3 mm. The polyamide-polyester complex take-up velocity is 800 m/min. After the first round of spinning the super micro fibers dimensions were determined as 13 denier per filament.

[0038] The polyesters (Component B & C) are melted and removed using 5% NaOH at 110° C. for sixty minutes. Using an electrical Hitachi electron scanning microscope, the final product, Nylon 6 fibers were determined to have dimensions of between 0.0014-0.003 denier per filament. See FIG. 1 in the figure section. The enlargement ratio of the figure is 5000.

EXAMPLE II

[0039] 50% by weight of Nylon 66 (Component A) with relative viscosity of 2.50. 40% by weight of copolyester (Component B) polyethylene terephthalate (PET) and 10% per mol of adipic acid. The intrinsic viscosity of the component B is 0.512. 10% by weight of copolyester (Component C) containing polyethylene terephthalate (PET), 10% per mol of isophthalic and 0.3% per mol of 5-sodium sulfodimethyl isophthalate. Component C has an intrinsic viscosity of 0.503. The blending and spinning conditions are similar to those practiced in example I. The spinneret pack pressure is 120 kg/cm² . The polyamide-polyester take-up velocity is 600 m/min. The polyesters (Components B & C) are melted and subsequently removed using NaOH. The Nylon 66 super micro fibers were determined to have dimensions of between 0.0035-0.0014 denier per filament. 

What is claimed; 5) [NEW] A method for manufacturing super-micro fibers comprising: (a) Blending polyamide-polyester mixtures containing the following: (i) 30-50% weight mixtures of polyamide compounds; (ii) 40-65% weight mixtures of terepthalic, ethylene glycol with diol and diacids or isophthalic compounds; (iii) 5-10% weight of affinity mixtures containing terephthalic acid, ethlylene glycol and 5-sodium sulfodimethyl isophthalate compounds; and, (b) Performing single-path, twin-screw extrusion of said polyamide-polyester mixtures; and, (c) Spinning said single-path, twin-screw, extrude polyamide-polyester mixtures; and, (d) Performing drawing processes of said single-path, extrude polyamide-polyester mixtures; and, (e) Melting, dissolving and removing sea-phase polyester components from said polyamide-polyester mixtures to form island-phase, polyamide, super-micro fiber components of 0.003-0.0003 denier per filament. 6) [NEW] A method for manufacturing super-micro fibers according to claim 5, wherein during the manufacturing method said 30-50% weight mixtures and said 40-65% weight mixtures has melting viscosity ratios of between 4-10. 7) [NEW] A method for manufacturing super-micro fibers according to claim 5, wherein said 40-65% weight mixtures has an addition ratio of between 5-40 mol%. 8) [NEW] A method for manufacturing super-micro fibers according to claim 6, wherein said 40-65% weight mixtures' intrinsic viscosity is maintained above 0.5. 9) [NEW] A method for manufacturing super-micro fibers according to claim 5, wherein 1% of said 5-sodium sulfodimethyl isophthalate is added to said 5-10% affinity mixtures. 10) [NEW] A method for manufacturing super-micro fibers according to claim 5, wherein spinning is performed at a spinneret pack pressure of 70 Kg/cm². 11) [NEW] A method for manufacturing super-micro fibers according to claim 5, wherein spinning is performed at a spinneret pack pressure of 70 Kg/cm² and a take-up velocity of between 600-1500 m/min. 12) [NEW] A method for manufacturing super-micro fibers according to claim 7, wherein alkaline solvents are used to separate the sea-phase components from the island-phase super-micro fiber products. 13) [NEW] A method for manufacturing super-micro fibers comprising: (a) Blending polyamide-polyester mixtures containing the following: (i) mixtures of polyamide compounds; (ii) mixtures of terepthalic, ethylene glycol with diol and diacids or isophthalic compounds; (iii) 5-10% weight of affinity mixtures containing terephthalic acid, ethlylene glycol and ≦1% 5-sodium sulfodimethyl isophthalate compounds; and, (b) Performing single-path, twin-screw extrusion of said polyamide-polyester mixtures; and, (c) Spinning said single-path, twin-screw, extrude polyamide-polyester mixtures; and, (d) Performing drawing processes of said single-path, extrude polyamide-polyester mixtures; and, (e) Melting, dissolving and removing sea-phase polyester components from said polyamide-polyester mixtures to form island-phase, polyamide, super-micro fiber components of 0.003-0.0003 denier per filament. 14) [NEW] A method for manufacturing super-micro fibers according to claim 13, wherein said mixture of polyamide compounds is 30-50% by weight. 15) [NEW] A method for manufacturing super-micro fibers according to claim 13, wherein said mixture of terpthalic, ethylene glycol with diol and diacids or isophthalic compound is 40-65% by weight. 16) [NEW] A method for manufacturing super-micro fibers according to claim 14, wherein said 40-65% weight mixtures has an addition ratio between 5-40 mol % and an intrinsic viscosity maintained above 0.5. 17) [NEW] A method for manufacturing super-micro fibers according to claim 16, wherein alkaline solvents are used to separate the sea-phase components from the island-phase super-micro fiber products. 18) [NEW] A method for manufacturing super-micro fibers according to claim 17, wherein spinning is performed at a spinneret packed pressure of 70 Kg/cm² and a take-up velocity of between 600-1500 m/min. 19) [NEW] A method for manufacturing super-micro fibers comprising: (a) Blending polyamide-polyester mixtures containing the following: (i) mixtures of polyamide compounds; (ii) mixtures of terepthalic, ethylene glycol with diol and diacids or isophthalic compounds; (iii) affinity mixtures containing terephthalic acid, ethlylene glycol and ≦1% 5-sodium sulfodimethyl isophthalate compounds; and, (b) Performing single-path, twin-screw extrusion of said polyamide-polyester mixtures; and, (c) Spinning said single-path, twin-screw, extrude polyamide-polyester mixtures; and, (d) Performing drawing processes of said single-path, extrude polyamide-polyester mixtures; and, (e) Melting, dissolving and removing sea-phase polyester components from said polyamide-polyester mixtures to form island-phase, polyamide, super-micro fiber components of 0.003-0.0003 denier per filament. 20) [NEW] A method for manufacturing super-micro fibers according to claim 19, wherein said mixture of polyamide compounds is 30-50% by weight, said mixture of terephthalic, ethylene glycol with diol and diacids or isophthalic compunds is 40-65% by weight and said affinity mixture is 5-10% by weight. 21) [NEW] A method for manufacturing super-micro fibers according to claim 20, wherein said 40-65% weight mixtures has an addition ratio between 5-40 mol % and an intrinsic viscosity maintained above 0.5. 22) [NEW] A method for manufacturing super-micro fibers according to claim 21, wherein spinnig is performed at a spinneret packed pressure of 70 Kg/cm² and a take-up velocity of between 600-1500 m/min. 23) [NEW] A method for manufacturing super-micro fibers according to claim 21, wherein alkaline solvents are used to separate the sea-phase components from the island-phase super-micro fiber products. 